Nanoscale analysis of the photodegradation of polyester fibers by AFM-IR

Formation of nanoparticles during accelerated UV degradation of fleece polyester textiles

Micro- and nanoplastics have emerged as critical pollutants in various ecosystems, posing potential environmental and human health risks. Washing of polyester textiles has been identified as one of the sources of nanoplastics. However, other stages of the textile life cycle may also release nanoparticles. This study aimed to examine nanoparticle release during UV degradation of polyester textiles under controlled and real-world conditions. Fleece polyester textiles were weathered under simulated sunlight for up to two months, either in air or submerged in water. We conducted bi-weekly SEM image analyses and quantified released nanoparticles using nanoparticle tracking analysis (NTA). At week 0, the fiber surface appeared smooth after prewashing. In the air group, nanoparticles appeared on the fiber surface after UV-exposure. In the group of textiles submerged in water, the surfaces developed more pits over time. The cumulative nanoparticle emission from the weathered textiles ranged from 1.4 × 1011 to 4.0 × 1011 particles per gram of fabric in the air group and from 1.6 × 1011 to 4.4 × 1011 particles per gram of fabric in the water group over two months. The predominant particle size fell into the 100 to 200 nm range. The estimated mass of the released nanoparticles was 0.06-0.26 g per gram of fabric, which is lower than the amount released during the washing of new textiles. Additionally, Scanning Transmission X-ray Microscopy (STXM) images indicated that the weathered nanoparticles underwent oxidation. Overall, the research offers valuable insights into nanoparticle formation and release from polyester textiles during UV degradation.

From cracks to secondary microplastics - surface characterization of polyethylene terephthalate (PET) during weathering

Secondary microplastics are a product of the fragmentation of plastic debris. Despite concerns regarding the omnipresence of microplastics in the environment, knowledge about the mechanics of their actual formation is still limited. Fragmentation is usually linked to weathering, which alters the properties of the plastic and allows fragmentation to occur. Therefore, in this study, polyethylene terephthalate (PET) samples were exposed to artificial UV light or a combination of UV light and water for a total of three months to simulate natural weathering. The samples included three forms of PET with different production histories: pellets, yarns, and films. The surface alterations to the samples during weathering were characterized using scanning electron microscopy and Raman spectroscopy. Results indicated that the three different types of PET developed markedly different surface defects and also exhibited signs of weathering within different time frames. Differences were also found between samples exposed only to UV and those exposed to UV and submerged in water. In water, the first surface changes were spotted within 30 days of initial submersion and later developed into an organized crack network. Upon the introduction of mild mechanical forces, pieces of the weathered surface started to delaminate. The fragments from films had an elongated shape with a median size of 16.1 × 2.1 × 1.8 μm, resembling a fibre. If the weathered surface of a film were to detach completely, it could create 1.4-7.9 million microplastic fragments/cm2. For pellets, this number would range between 0.4 and 2.2 million microplastics/cm2. In addition to particle formation by surface delamination, particles also emerged on the weathered surfaces of all studied samples, presenting another possible source of micro-sized particles during weathering. Overall, the results of this work show that the weathering of plastics and the formation of microplastics are heavily influenced not only by the weathering mechanism but also by the type and production history of the polymers.

Influence of Aging on the Physical Properties of Knitted Polymeric Materials

Nowadays, as consumer expectations have increased worldwide, the importance of polymer materials performance has been raised to a new level. Efforts are required to produce a high-quality product that maintains its quality despite aging factors in certain geographical locations. In the experimental part of this study, polyester materials produced from conventional and recycled yarns, further intended for the production of sportswear, were exposed to natural weathering. Before and after the exposure, the following material properties were investigated: material surface appearance, material thickness, mass per unit area, horizontal and vertical density, surface roughness, tensile properties (force at break, elongation at break), water vapor permeability, liquid dispersion and drying of the material. The results indicate that the surface mass and thickness of all exposed polyester materials decreased after aging due to material shrinkage. The results indicated that prolonged aging negatively affected the values of elongation and force at break. The recycled material exhibited the highest overall decreases in elongation and force at break, but lower surface roughness. In addition, recycled material exhibited a shorter drying time than that of conventional material, both before and after aging.

Time-resolved vibrational dynamics: Novel opportunities for sensing and imaging

The evolution of time-resolved spectroscopies has resulted in significant advancements across numerous scientific disciplines, particularly those concerned with molecular electronic states. However, the intricacy of molecular vibrational spectroscopies, which provide comprehensive molecular-level information within complex structures, has presented considerable challenges due to the ultrashort dephasing time. Over recent decades, an increasing focus has been placed on exploring the temporal progression of bond vibrations, thereby facilitating an improved understanding of energy redistribution within and between molecules. This review article focuses on an array of time-resolved detection methodologies, each distinguished by unique technological attributes that offer exclusive capabilities for investigating the physical phenomena propelled by molecular vibrational dynamics. In summary, time-resolved vibrational spectroscopy emerges as a potent instrument for deciphering the dynamic behavior of molecules. Its potential for driving future progress across fields as diverse as biology and materials science is substantial, marking a promising future for this innovative tool.

Releases of microplastics and chemicals from nonwoven polyester fabric-based polyurethane synthetic leather by photoaging

The nonwoven PET fabrics are chemically, mechanically and thermally treated fiber aggregate without weaving, knitting or braiding, which could be used as a base to make polyurethane (PU) synthetic leather through a series of processing. Our research systematically compared the photoaging behaviors of pure non-woven PET base fabric (NPET-P) and PU synthetic leather (nonwoven PET-base fabrics with PU coating, NPET-U), and their possibilities for microplastic fibers (MPFs) generation and chemical transformation in water. NPET-U was photoaged to a higher oxidation degree with higher O/C ratios and more distinct changes in chemical structures. The amount of MPFs released from NPET-U (1.98 × 107 g/fibers) was significantly lower than that from NPET-P (4.76 × 107 g/fibers) after 360 h light irradiation (p value <0.05) with a slower degradation rate and delayed MPFs release. The lengths and diameters of released MPFs from NPET-U varied within a smaller range than that from NPET-P exposed to UV light irradiation. Natural sunlight aging of fabrics for 365 days was found to be equivalent to approximately 85.3-127.2 h UV aging in the laboratory, which indicated the lab accelerated experiments was extraordinarily intense to simulate natural sunlight aging. Furthermore, abundant calcium and sulfur-contained chemicals were detected in original fabrics and the leachate of 360 h light-aged fabrics using the inductively coupled plasma optical emission spectrometer (ICP-OES). The organic components of the leachate were separated according to their molecular weight with the changes of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and the UV response over aging time. UV stimulation aggravated the role of plastic polymers as disinfection by-product (DBP) precursors. Nevertheless, although NPET-U could produce more nitrogen-contained chemicals, it had similar formation potentials of nitrogen-containing DBPs as NPET-P. The discussion lucubrated the potential risks of the production of MPFs and chemical release in the leachate with regard to combined plastic pollution.

Low environmental impact remediation of microplastics: Visible-light photocatalytic degradation of PET microplastics using bio-inspired C,N-TiO2/SiO2 photocatalysts

Microplastics (MPs) are plastic particles with sizes between 1 μm and 5 mm with a ubiquitous presence in aquatic ecosystems. MPs harm marine life and can cause severe health problems for humans. Advanced oxidation processes (AOPs) that involve the in-situ generation of highly oxidant hydroxyl radicals can be an alternative to fight MPs pollution. Of all the AOPs, photocatalysis has been proven a clean technology to overcome microplastic pollution. This work proposes novel C,N-TiO₂/SiO₂ photocatalysts with proper visible-active properties to degrade polyethylene terephthalate (PET) MPs. Photocatalysis was performed in an aqueous medium and at room temperature, evaluating the influence of two pH values (pH 6 and 8). The results demonstrated that the degradation of the PET MPs by C,N-TiO₂/SiO₂ semiconductors is possible, achieving mass losses between 9.35 and 16.22 %.

Characterization of fiber fragments released from polyester textiles during UV weathering

Synthetic textiles are considered a prime source of microplastics fibers which are a prevalent shape of microplastic pollution. Whilst the release mechanisms and formation of such microplastic fibers have been so far mainly studied in connection with laundry washing, there are some studies emerging that describe also other release pathways for microplastic fibers such as abrasion during wearing. The aim of this study was to consider weathering as another process contributing to the formation of microplastic fibers and their presence in the environment. Four types of polyester fabrics were selected and exposed to artificial weathering by UV-light for two months. The fabrics were extracted every 15 days to quantify and characterize the formed microplastics. Microplastic fibers with the diameter matching the size of the fibers in the textiles were observed. However, additional microplastic fibers of different shapes were also formed. These included partially broken fibers, thin fibers with a diameter below the size of the fiber in the fabrics, fibers flattened into a ribbon, and non-fibrous microplastics. The released microplastics evinced physical alterations on their surface in the form of pits and cracks. The released microplastics exhibited a steep increase in number with progressing weathering; from hundreds of fibers per gram of textile from unaged fabrics, to hundred thousands fibers (150,000-450,000 MPF/g) after 2 months of weathering. Additional 10,000-52,000 unfibrous microplastics/g were released from the weathered fabrics. While plain fabrics showed higher releases than interlock and fleece, further research is needed to evaluate the importance of the textile architecture on the weathering process in comparison with the production history of the fabrics. Based on a comparison with washing studies with the same textiles, we can estimate that the potential of weathered fabrics to be a source of microplastic fibers can be 20-40 times larger than washing only.

The Effect of Accelerated Aging on the Molecular Weight and Thermal and Mechanical Properties of Polyester Yarns Containing Ceramic Particles

The accelerated aging of polyethylene terephthalate (PET) multifilament yarns containing nano or microparticles of titanium dioxide (TiO2), silicon carbide (SiC), or fluorite (CaF2) at a maximum percentage of 2% has been studied. For this, the yarn samples were introduced into a climatic chamber at 50 °C, 50% relative humidity, and an ultraviolet A (UVA) irradiance of 1.4 W/m2. They were then removed from the chamber after periods of between 21 and 170 days of exposure. Subsequently, the variation in weight average molecular weight, number molecular weight, and polydispersity was evaluated by gel permeation chromatography (GPC), the surface appearance was evaluated using scanning electron microscopy (SEM), the thermal properties were evaluated using differential scanning calorimetry (DSC), and the mechanical properties were evaluated using dynamometry. The results showed that, at the test conditions, there was degradation in all of the exposed substrates, possibly due to the excision of the chains that make up the polymeric matrix, which resulted in the variation in the mechanical and thermal properties depending on the type and size of the particle used. This study provides insight into the evolution of the properties of PET-based nano- and microcomposites and might be helpful when selecting materials for specific applications, which is of great interest from an industrial point of view.

Design and Analysis of a Novel Ultraviolet-C Device for Surgical Face Mask Disinfection

This paper deals with the design of a compact sanitization device and the definition of a specific protocol for UV-C disinfection of a surgical face mask. The system was designed considering the material properties, face mask shape, and UV-C light distribution. DIALux software was used to evaluate the irradiance distribution provided by the lamps emitting in the UV-C range. The irradiance needed for UV-C-decontaminated bacteria and virus, and other contaminating pathogens, without compromising their integrity and guaranteeing inactivation of the bacteria, was evaluated. The face mask's material properties were analyzed with respect to UV-C exposure in terms of physicochemical properties, breathability, and bacterial filtration performance. Information on the effect of time-dependent passive decontamination at room temperature storage was provided. Single and multiple cycles of UV-C sanitization did not adversely affect respirator breathability and bacterial filtration efficiency. This multidisciplinal approach may provide important information on how it is possible to correctly sanitize a face mask and, in case of shortage, safely reuse the face mask.

Ignored microplastic sources from plastic bottle recycling

The recovery and recycling of plastic products has increased dramatically in recent years as a strategy to achieve sustainable production and minimization of plastic pollution. However, the release of microplastics during plastic recycling has received little attention. We evaluated the generation and fate of microplastics in three typical facilities which make polyethylene terephthalate (PET) flakes using post-consumer PET bottles as raw material. Microplastics, 0.1- 5.0 mm in size, were detected in production wastewater at concentrations ranging from 23.43 ± 1.04 mg/L to 1836.37 ± 31.73 mg/L, while decreased to (8.13 ± 0.42-83.83 ± 0.93) mg/L in discharge effluent and (52,166 ± 2858-68,866 ± 2500) μg/g in sludge. Interestingly, the profiles of microplastics in samples from production wastewater, effluents, and sludge showed significant differences. Although, in all three compartments, the mass of microplastics increased, and the particle number decreased with increasing particle size. Overall, the removal ratio of total microplastics from the production wastewater was 53.47 ± 4.48% to 99.56 ± 0.02% in mass, and from 90.08 ± 0.82% to 99.56 ± 0.05% in quantity. The loss of microplastics from wastewater resulted in their concentration in sludge. Factors that influence the transfer of microplastics from wastewater to sludge should be identified and utilized to maintain a high level of removal and prevent leakage of these particles into the environment.

A Review on Synthetic Fibers for Polymer Matrix Composites: Performance, Failure Modes and Applications

In the last decade, synthetic fiber, as a reinforcing specialist, has been mainly used in polymer matrix composites (PMC’s) to provide lightweight materials with improved stiffness, modulus, and strength. The significant feature of PMC’s is their reinforcement. The main role of the reinforcement is to withstand the load applied to the composite. However, in order to fulfill its purpose, the reinforcements must meet some basic criteria such as: being compatible with the matrix, making chemical or adhesion bonds with the matrix, having properties superior to the matrix, presenting the optimal orientation in composite and, also, having a suitable shape. The current review reveals a detailed study of the current progress of synthetic fibers in a variety of reinforced composites. The main properties, failure modes, and applications of composites based on synthetic fibers are detailed both according to the mentioned criteria and according to their types (organic or inorganic fibers). In addition, the choice of classifications, applications, and properties of synthetic fibers is largely based on their physical and mechanical characteristics, as well as on the synthesis process. Finally, some future research directions and challenges are highlighted.

Surface Characteristics and Color Stability of Dental PEEK Related to Water Saturation and Thermal Cycling

(1) Background: The study was undertaken to evaluate the surface characteristics, microhardness, and color stability of PEEK materials related to water saturation and in vitro aging. (2) Methods: Custom specimens of unmodified and modified PEEK CAD/CAM materials were investigated: BioHPP, a ceramic reinforced PEEK, and Finoframe PEEK and Juvora medical PEEK, 100% PEEK materials. Forty-eight plates were sectioned in rectangular slices. The specimens were immersed in distilled water at 37 °C for a period of 28 days, and then subjected to aging by thermal cycling (10,000 cycles). Surface roughness was measured with a contact profilometer; nanosurface topographic characterization was made by Atomic Force Microscopy; Vickers hardness measurements were performed with a micro-hardness tester; color changes were calculated. All registrations were made before immersion in water and then subsequently once a week for 4 weeks, and after thermocycling. (3) Results: The studied reinforced and unfilled PEEK materials reached water saturation after the first week of immersion, without significant differences between them. The most affected from this point of view was the reinforced PEEK material. Thermocycling induces a significant increase inmicroroughness, without significant differences between the studied materials. In relation to the nanosurface topography and roughness, the reinforced PEEK material was the least modified by aging. The color changes after 4 weeks of water immersion and one year of simulated in vitro aging ranged from extremely slight to slight, for all materials. (4) Conclusions: Water absorption was associated with a decrease in microhardness. Surface characteristics are affected by water immersion and thermocycling. Perceivable or marked color changes of the materials were not detected during the study.

Optical Behavior and Surface Analysis of Dental Resin Matrix Ceramics Related to Thermocycling and Finishing

Color preservation of esthetic dental restorative materials in the oral environment represents, besides longevity, a concern, and there is still limited knowledge related to the effect of aging on the optical behavior of resin matrix ceramics. The study analyzed the finishing and thermocycling of resin matrix ceramic material surfaces, in order to assess their consequences on optical properties. Five resin matrix CAD/CAM ceramics, namely a polymer-infiltrated ceramic and four types of nanoparticle-filled resins, were selected for the study, and finished by polishing and glazing. Thermocycling was chosen as the in vitro aging method. Surface microroughness, optical and hardness evaluations were achieved before and after artificial aging. Statistical analyses were performed with IBM SPSS Statistics software at a significance value of p < 0.05. Micro-roughness values increased after thermocycling, but were kept under the clinically accepted values. The optical characteristics of resin matrix ceramics were not significantly modified by thermocycling. Values of the glazed samples became closer to those of the polished ones, after hydrothermal aging, even if the differences were insignificant. Thermocycling significantly decreased the microhardness, mainly for glazed samples. This could be the consequence of glaze removal during thermocycling, which means that glazes provide a surface protection for a limited time.

Evaluation of Changes in Polymer Material Properties Due to Aging in Different Environments

With the increase in awareness of the importance of engagement in physical activities, high requirements have been placed on polymers intended for use in sports. A number of authors investigated the influence of aging factors on the performance of the polymer. Still, there is a lack of aging protocols that would be product-centered, especially when high performance is imperative. This paper presents a new approach to polymer aging and examines the change of the identified set of properties due to aging under different conditions, and the duration of each (topography, thickness, moisture management, elongation, and bursting force). The results of the testing revealed the increase in thickness due to exposure, especially to the sun-exposed materials. The ability of materials to elongate until the moment of rupture decreases due to exposure to the sun (strong relationship to the time of exposure; R2 reaches 0.99) and the bursting force (up to 6.8%). Furthermore, results indicate the significantly impaired capacity of the polymer material to absorb moisture. The results of measurements indicated (derived) by spectroscopic studies, based on the ATR-FTIR (attenuated total reflectance) method, showed that there was no detectable influence of aging in the sun or shade on the chemical structure of polyester samples.

Masking Abilities of Dental Cad/Cam Resin Composite Materials Related to Substrate and Luting Material

An outstanding treatment challenge related to aesthetic monolithic materials is to mask discolored substrates in aesthetic areas. The purpose of the study is to evaluate the substrate masking ability of different resin composite materials and the influence of their association with luting agents and substrates. Five types of 2M2 HT (high translucency) resin composite materials were selected: Vita Enamic [E] and four types of nanoparticle-filled composites Lava Ultimate [L], Cerasmart [C], Shofu HC [S], and Hyramic [H]. Resin composite Vita VM LC with different shades was used for the substrates: 2M2, 3M2, and CP2. Variolink Esthetic Try-inpastes neutral, light+, and warm+ colors were chosen to simulate the luting agent color. Optical parameters (TP (translucency), CR (contrast ratio), and OP (opalesce)) and color differences ΔE (chromatic difference) were calculated. Statistical analyses were performed to evaluate the comparisons between the groups and establish correlations. TP average values for all materials were in the range of 21.49–24.53. OP average values were in the rage of 6.31–7.85. OP is moderate positive correlated to TP and CR is negative and strong correlated to TP. Related to materials, average color changes decrease as following: E > H > C > L > S. Referring to the tryin material, warm colors induce marked color changes of the restoration. The differences of the color changes determined by all studied substrates are significant. For the final aesthetic aspect of the restoration, it is essential to consider the underlying dental structure, luting agent, and restoration material as a whole unit. The masking ability of the investigated resin matrix ceramic materials materials shows differences, the best behavior demonstrated Shofu HC and Lava Ultimate. Marked color changes are related to high chroma substrates. For substrates with a darker color, the association with warm try-in pastes lead to marked color changes, but with neutral and light try-in pastes at most perceivable.

Probing the Nanoscale Heterogeneous Mixing in a High-Performance Polymer Blend

The blend of polyetheretherketone (PEEK) and polybenzimidazole (PBI) produces a high-performance blend (PPB) that is a potential replacement material in several industries due to its high temperature stability and desirable tribological properties. Understanding the nanoscale structure and interface of the two domains of the blend is critical for elucidating the origin of these desirable properties. Whilst achieving the physical characterisation of the domain structures is relatively uncomplicated, the elucidation of structures at the interface presents a significant experimental challenge. In this work, we combine atomic force microscopy (AFM) with an IR laser (AFM-IR) and thermal cantilever probes (nanoTA) to gain insights into the chemical heterogeneity and extent of mixing within the blend structure for the first time. The AFM-IR and nanoTA measurements show that domains in the blend are compositionally different from those of the pure PEEK and PBI polymers, with significant variations observed in a transition region several microns wide in proximity to domain boundary. This strongly points to physical mixing of the two components on a molecular scale at the interface. The versatility intrinsic to the combined methodology employed in this work provides nano- and microscale chemical information that can be used to understand the link between properties of different length scales across a wide range of materials.

Unexpected Susceptibility of Poly(ethylene furanoate) to UV Irradiation: A Warning Light for Furandicarboxylic Acid?

Poly(ethylene furanoate) (PEF) is widely advocated as a renewable alternative to the fossil-based polyester poly(ethylene terephthalate) (PET). Whereas the UV stability of PET is well-studied, little is known for PEF. Here, we compare the UV stability of both polyesters after 500 h of UV irradiation in a Q-SUN xenon arc chamber. Both the virgin and irradiated polyesters were characterized by FTIR, SEC, DSC, NMR, TGA, and MALDI-TOF MS. PET showed only minor signs of degradation under the applied test conditions, while PEF showed significant discoloration as well as evidence of both cross linking/chain extension and chain scission. Also, the thermal properties and the ability to crystallize of PEF were severely impacted by UV irradiation. Although a detailed study on the degradation mechanism is out of the scope of this work, we found indications that Norrish type I and II degradation reactions play an important role in the UV degradation of PEF.

Optical Properties and Color Stability of Dental PEEK Related to Artificial Ageing and Staining

Considering that the processes of PEEK discoloration caused by either intrinsic or extrinsic factors require elucidation, the aim of this study was to investigate the long-term effect of the combined action of ageing and immersing solutions on the optical properties and color stability of PEEK material, related to surface processing (polishing or glazing). (2) Methods: This study aims to determine the influence of different ageing and staining protocols on optical properties, color changes, and surface roughness of a reinforced PEEK material (bioHPP, Bredent, Senden, Germany). For ageing, specimens were submitted to 5000 cycles in a 55 °C bath and a 5 °C bath filled with distilled water. For staining, thermal cycling was performed in a hot coffee bath (55 °C) and a bath filled with distilled water (37 °C) and in a cold juice bath (5 °C) and a bath filled with distilled water (37 °C). Translucency (TP) and opalescence (OP) parameters were determined, the total color change value (ΔΕ*) was calculated, specimens’ surface roughness was analyzed, and statistical analyses were performed. (3) Results: The mean TP values of the studied samples were in the interval of 1.25–3.60, which is lower than those reported for natural teeth or other aesthetic restoration materials. The OP values of PEEK were registered in the range of 0.27–0.75, being also lower than those of natural teeth or other aesthetic restoration materials. OP has a very strong positive relationship with TP. The mean registered Ra values for all subgroups were below 0.13 µm. Artificial ageing and staining in hot coffee proved to increase the roughness values. (4) Conclusions: The glazing of PEEK has a favorable effect on surface roughness and opalescence, irrespective of the artificial ageing or staining protocols. Artificial ageing damages the color stability and roughness of PEEK, regardless of surface processing, and decreases the translucency and opalescence of glazed surfaces. Immersion in hot coffee leads to perceivable discolorations.

Behavior of Polymer Materials Exposed to Aging in the Swimming Pool: Focus on Properties That Assure Comfort and Durability

The degradation of polyamide (PA) and polyester (PES) polymers is under intense study due to growing concerns about the accumulation of plastics in soils and oceans. Previous studies confirm that ageing degrades PA and PES at the molecular level. However, researchers have not addressed the development of protocols for aging textile materials in swimming pools, and few data are available on the effects of aging on comfort and durability. This research addresses the development of the aging protocol for PA and PES swimwear materials, its implementation, and the evaluation of properties that assure comfort and durability after specific periods of exposure. The tests include microscopic analysis, tensile tests, determination of fluid transport phases and drying period. The results revealed changes in the surface of the material in terms of fibrillation (more pronounced after outdoor aging). There is a positive correlation between the exposure duration and the breaking force (R² ranges from 0.85 to 0.98), with a stronger correlation for the PA materials. The decrease in breaking force due to aging is up to 40%, indicating significantly reduced durability. The change in breaking force follows the changes in mass (R² = 0.867). In terms of comfort assurance, outdoor aging of materials should have a greater negative impact than indoor ageing.

Photocatalytic aging process of Nano-TiO2 coated polypropylene microplastics: Combining atomic force microscopy and infrared spectroscopy (AFM-IR) for nanoscale chemical characterization

Microplastics (MPs) are considered to have greater environmental hazards than large plastics. Most MPs undergo different degrees of aging and aged MPs exhibit different physicochemical properties from pristine ones. This study successfully prepared a nano-TiO₂ coated polypropylene MPs, and explored the nanoscale infrared, thermal, and mechanical properties of MPs before and after photo-aging using a combined AFM-IR technique. Surface height range of MPs was ± 25 nm. The signal intensity of the absorption peak at 1654 cm^-1 in terms of vinylidene end groups gradually increased as the irradiation time prolonged. The softening temperature of MPs decreased from 126.7 °C to 108.5 °C as the irradiation time increased from 0 h to 4 h. The MPs after photo-aging became stiffer, especially for the components surrounding the nano-TiO₂ particle, indicating that photocatalytic reaction accelerated the aging process of MPs. The resonance frequency of MPs surrounding the nano-TiO₂ particle was stronger after photo-aging and the stiffer components were uniformly distributed, confirming that the thermal and mechanical properties of MPs changed after photo-aging. These novel findings are essential to better understand the changes in the surface microstructures, physical properties, and chemical compositions of MPs during aging process.

Nanoscale Infrared Spectroscopy and Chemometrics Enable Detection of Intracellular Protein Distribution

Determination of the intracellular location of proteins is one of the fundamental tasks of microbiology. Conventionally, label-based microscopy and super-resolution techniques are employed. In this work, we demonstrate a new technique that can determine intracellular protein distribution at nanometer spatial resolution. This method combines nanoscale spatial resolution chemical imaging using the photothermal-induced resonance (PTIR) technique with multivariate modeling to reveal the intracellular distribution of cell components. Here, we demonstrate its viability by imaging the distribution of major cellulases and xylanases in Trichoderma reesei using the colocation of a fluorescent label (enhanced yellow fluorescence protein, EYFP) with the target enzymes to calibrate the chemometric model. The obtained partial least squares model successfully shows the distribution of these proteins inside the cell and opens the door for further studies on protein secretion mechanisms using PTIR.

Graphene Oxide-Induced Interfacial Transcrystallization of Single-Fiber Milkweed/Polycaprolactone/Polyvinylchloride Composites

Understanding the interfacial crystallization is crucial for semi-crystalline polymer/natural fiber composites because it links to the final properties. This work reports, for the first time, the interfacial crystallization of a miscible blend between polycaprolactone (PCL) and polyvinylchloride (PVC) with milkweed fibers. We have first described the morphology of the fibers and the chemical composition of waxes covered on its surface. Our findings show that the transcrystallization (TC) layer of PCL/PVC could appear at the interface by simply coating with a layer of graphene oxide (GO) on the milkweed fiber. In our study, atomic force microscopy-infrared spectroscopy analysis shows that the crystallinity of the blends is higher at the vicinity of the interface compared to that in the bulk. The kinetic of the interfacial crystallization in terms of spherulite morphology and crystal growth rates at the nanoscale is examined. X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy were used to analyze the prepared GO and evaluate its relationship with the interfacial crystallization behavior of the blends.

Surface Quality Evaluation of Removable Thermoplastic Dental Appliances Related to Staining Beverages and Cleaning Agents

(1) Background: Thermoplastic materials are not inert and subject to changes in the oral environment, which affect their surface quality. Color stability and topographic characteristics of clear thermoplastic appliances are critical considerations. The study aimed to evaluate the optical changes and surface topography of different thermoplastic materials related to staining beverages and cleaning agents. (2) Methods: Thermoplastic polyethylene terephthalate glycol (PET-G) material specimens were selected for the study: S (Duran, Scheu-Dental GmbH, Iserlohn, Germany), D (Biolon, Dreve Dentamid GmbH, Unna, Germany), and B (Crystal, Bio Art Dental Equipment, Sao Carlos, Brazil). Four different media were involved for immersion: coffee (C) and black tea (T) at 55 °C, Coca-Cola (K) at 5 °C, and distilled water (W) at 22 °C. As for cleaning, chemical options and mechanical brushing were selected (P-powder, T-tablets, and X-brushing). Color changes, and mean surface roughness were measured at 24 h, 48 h, and after 7 days. Statistical analysis was performed. After the testing period, atomic force microscopy (AFM) analyses and SEM images were registered in order to characterize the surface topography. (3) Results: Quantitative color change evaluations revealed a slight change in color after 24 h and an extremely marked change after 48 h, respective 7 days. Mean roughness values are kept below the clinically acceptable limit of 0.20 µm for all samples. Related to mean nanoroughness values Sa, and 3D evaluations of the surface quality, Biolon samples have demonstrated the most constant behavior, while Crystal samples are visibly influenced by water immersion. Related to the cleaning method, the topography of Duran samples was influenced by mechanical brushing. (4) Conclusions: Nanoscale investigations provided high accuracy and more realistic surface quality examinations of the examined samples compared to profilometry. Both SEM and AFM should be used for a more detailed description of the surface topography.

Reflectance in AFM-IR: Implications for Interpretation and Remote Analysis of the Buried Interface

AFM-IR combines the chemical sensitivity of infrared spectroscopy with the lateral resolution of scanning probe microscopy, allowing nanoscale chemical analysis of almost any organic material under ambient conditions. As a result, this versatile technique is rapidly gaining popularity among materials scientists. Here, we report a previously overlooked source of data and artifacts in AFM-IR analysis; reflection from the buried interface. Periodic arrays of gold on glass are used to show that the overall signal in AFM-IR is affected by the wavelength-dependent reflectivity and thermal response of the underlying substrate. Excitingly, this demonstrates that remote analysis of heterogeneities at the buried interface is possible alongside that of an overlying organic film. On the other hand, AFM-IR users should carefully consider the composition and topography of underlying substrates when interpreting nanoscale infrared data. The common practice of generating ratio images, or indeed the normalization of AFM-IR spectra, should be approached with caution in the presence of substrate heterogeneity or variable sample thickness.

Recent Applications of Advanced Atomic Force Microscopy in Polymer Science: A Review

Atomic force microscopy (AFM) has been extensively used for the nanoscale characterization of polymeric materials. The coupling of AFM with infrared spectroscope (AFM-IR) provides another advantage to the chemical analyses and thus helps to shed light upon the study of polymers. This paper reviews some recent progress in the application of AFM and AFM-IR in polymer science. We describe the principle of AFM-IR and the recent improvements to enhance its resolution. We also discuss the latest progress in the use of AFM-IR as a super-resolution correlated scanned-probe infrared spectroscopy for the chemical characterization of polymer materials dealing with polymer composites, polymer blends, multilayers, and biopolymers. To highlight the advantages of AFM-IR, we report several results in studying the crystallization of both miscible and immiscible blends as well as polymer aging. Finally, we demonstrate how this novel technique can be used to determine phase separation, spherulitic structure, and crystallization mechanisms at nanoscales, which has never been achieved before. The review also discusses future trends in the use of AFM-IR in polymer materials, especially in polymer thin film investigation.

Antibacterial Activity of TiO2- and ZnO-Decorated with Silver Nanoparticles

This work emphasizes the use of the silver decorative method to enhance the antibacterial activity of TiO2 and ZnO nanoparticles. These silver-decorated nanoparticles (hybrid nanoparticles) were synthesized using sodium borohydride as a reducing agent, with the weight ratio of Ag precursors/oxide nanoparticles = 1:30. The morphology and optical properties of these hybrid nanoparticles were investigated using transmission electron microscopy (TEM), X-ray diffraction (XRD) patterns, and UV-Vis spectroscopy. The agar-well diffusion method was used to evaluate their antibacterial activity against both Staphylococcus aureus and Escherichia coli bacteria, with or without light irradiation. The TEM images indicated clearly that silver nanoparticles (AgNPs, 5–10 nm) were well deposited on the surface of nano-TiO2 particles (30–60 nm). In addition to this, bigger AgNPs (<20 nm) were dispersed on the surface of nano-ZnO particles (30–50 nm). XRD patterns confirmed the presence of AgNPs in both Ag-decorated TiO2 and Ag-decorated ZnO nanoparticles. UV-Vis spectra confirmed that the hybridization of Ag and oxide nanoparticles led to a shift in the absorption edge of oxide nanoparticles to the lower energy region (visible region). The antibacterial tests indicated that both oxide pure nanoparticles did not exhibit inhibitory effects against bacteria, with or without light irradiation. However, the presence of AgNPs in their hybrids, even at low content (<40 mg/mL), leads to a good antibacterial activity, and higher inhibition zones under light irradiation as compared to those in dark were observed.

Butyl Rubber-Based Composite: Thermal Degradation and Prediction of Service Lifetime

Butyl rubber-based composite (BRC) is one of the most popular materials for the fabrication of protective gloves against chemical and mechanical risks. However, in many workplaces, such as metal manufacturing or automotive mechanical services, its mechanical hazards usually appear together with metalworking fluids (MWFs). The presence of these contaminants, particularly at high temperatures, could modify its properties due to the scission, the plasticization and the crosslinking of the polymer network and thus lead to severe modification of the mechanical and physicochemical properties of material. This work aims to determine the effect of temperature and a metalworking fluid on the mechanical behavior of butyl rubber composite, dealing with crosslinking density, cohesion forces and the elastic constant of BRC, based on Mooney–Rivlin’s theory. The effect of temperature with and without MWFs on the thermo-dynamical properties and morphology of butyl membranes was also investigated. The prediction of service lifetime was then evaluated from the extrapolation of the Arrhenius plot at different temperatures.

Biological Activity and Nanostructuration of Fe3O4-Ag/High Density Polyethylene Nanocomposites

We report here the synthesis of uniform nanospheres-like silver nanoparticles (Ag NPs, 5–10 nm) and the dumbbell-like Fe3O4-Ag hybrid nanoparticles (FeAg NPs, 8–16 nm) by the use of a seeding growth method in the presence of oleic acid (OA)/oleylamine (OLA) as surfactants. The antibacterial activity of pure nanoparticles and nanocomposites by monitoring the bacterial lag–log growth has been investigated. The electron transfer from Ag NPs to Fe3O4 NPs which enhances the biological of silver nanoparticles has been proven by nanoscale Raman spectroscopy. The lamellae structure in the spherulite of FeAg NPs/High Density Polyethylene (HDPE) nanocomposites seems to play the key role in the antibacterial activity of nanocomposites, which has been proven by nanoscale AFM-IR. An atomic force microscopy coupled with nanoscale infrared microscopy (AFM-IR) is used to highlight the distribution of nanoparticles on the surface of nanocomposite at the nanoscale. The presence of FeAg NPs in PE nanocomposites has a better antibacterial activity than that reinforced by Ag NPs due to the faster Ag+ release rate from the Fe3O4-Ag hybrid nanoparticles and the ionization of Ag NPs in hybrid nanostructure.